Polymerization process employing a perfluorochlorocarboxylic acid as an emulsifying agent



United States Patc Q 2,374,152: POLYMERIZAT-IONTROGESS EMPLOYING A PER- FLUOROCIH'JOROCARBOXY-LIC. ACID AS AN EMULSIFYING AGENT Archibald N. Bolstad, Maplewood, andrRalphL. Herbst;, In, Westfield, .N. Jr, assignors by mesnewassignmcntsa to Minnesota Miniiig and lvfiinufacturing Company; St..Paul,.Minn., a corporation of Delaware NotDrawing: ApplicatiomflctoherrlS, 195 4 a Serial'Not463,073- L scams; (Cl. 260 -9211) lubricant or insulating medium. The waxes of chlorotrifluoroethylene are also usefulinthe preparation of lubri: cating'comp'ositionsandas impregnants for variouslinas terials. The solid polymer of chlorotrifluoroetliyl'etie in the high molecular weight. range-. has the' characteristics of a thermoplastic and is useful for. a variety of purposes: for" which plastics"maybe-employed;

It=is conventional practice to'"polymerize perhaloolefi'ns. such as chl'orotrifluoroethyl'ene using water suspension type'catalyst syste'msyfor example, a redbx catalystlsysterm this systemincl'irding an'oxidant and"areductant. The oxidant istgenerally anihorganic 'persulfate, andthe reductant is generally a'bisu'lfite: In these systems, it is also conventional practice to include a variable valence metal salt,v such" as frroussulfate? or ferrousnitrate', which. isaemployed'as; ani. activatorzt. However; the -use of such. variable:- valencevmeta'li salts: is; undesirable": for at numberofireasons. One: ohthecprimary reasons such salts? are undesirable is. that. the' activator. cation; such as the ferrous ion, contaminates the:polymercproductnwith the result that the} final pressed. polymer: sheets: armoft'en discolored; Theepressed. sheets may. range in color from. tan. to brown.- and may be spotted, whereas-tit is? desired tozproducesheets: whichwarercompletelycolorless;

In. ourcopendingapplication. Serial; No; 463,072; filed: Qctober l8, 1954;, there. isvdiscloseda: process? in whiclii afsubstituted ethylene" containing at. least. two; fluorine; atoms, and. preferablyat least onefluorine atomipen;

2,874,152 Patented Feb. 17, 1959 absenceoftcolor ninzhigher yieldstthanadoes :the process of oun copendingrapplication: Serial No; 463,072, filedOctober:18;,.19.5:4. Thezpo'lymersnmay beeither liquids;.waxes, onsolidsatheprocess:beiugaefiected in either a batchwise or; continuousv mannen;

- The monomer "is .aadinixed: withgthe= aqueous; suspension. mediumx in. a-. polymerizationzone which maintained under. the appropriate: conditions. of polymerization and under sufficient.pressurewto maintain theiaqueoussolution asea. liquidunder. tires-polymerization: conditions. The monomer. and .waterareragitated by, suitable meansin thev reaction zone-in order toxintimately disperse themonomer.

and. the: aqueous suspension. mediurm. The monomer anrl thepolymerproduced are bothsubstantially insoluble in the aqueous dispersion medium; hence, the separation oitherp olymerironr therwatert phase may-be effected by settling and decantation, by filtering, by centrifuging, by

evaporatiomof the: aqueousaphase, orv by other conventionaLmeans. known-- to the art, depending upon whether the. polymer vis inthe,liguid orsolid state.

, 'Ehepresent: inventionis, particularlyapplicable to the polymerization. of perfluorochloroolefins'such as chlorotrifluoroethylene, but the polymerization of I various other halogenated. olefins, is.alsor contemplated. These olefins include for .cxample perfluorobutadiene, perfluoropropene phenyltrifiuoroethylene, alpha methyl phenyl diflimroethylene, perfluoroacrylonitrile, perfluorocyclo hutadi'ene, tetrafluoroethylene, vinylidene. fluoride; tri-- fluoroethylene, and.difluorodichloroethylene. The invention appliesrto. the copolIymerizationv of. these andother monomers. as.,we1'1 as to. their homopolymerization. For.

1 example tlie. invention. appliestc. the cop olyrnerization' of"ehlbtotrifiuoroethylene and tetrafluoroethylene, ,chlorocarbon atom of the aliphatic portion of: theasubstitutedz ethylene, isv polymerized in. an? aqueous-: suspension; type catalyst system, which. is-preferably aredoxzcatalyst:.sys.atem. comprising, an oxidant, and; a vreductant but. in. the: absence of avariable valence rnetalsalh,and employing; a perfiuorochlorocarboxylic acid: as an emulsifying: agent.

In, accordance. with. the: present invention a substituted". ethylene containing at least two fluorineatorns preferably atleast one fluorine atom. percarbomatom of. the? aliphatic portionloflthe substituted ethylene, istpolymerizeda in an aqueoussuspension type catalyst system whichtisi: preferably, atred'ox. catalyst .system comprising an t oxidant but in the absence of both, a reductant-and avva'riable valence metal *salt,.. and employing, a perfluorochloroe carboxylic acid. asan. emulsifying; agent; The -process. of the invention produces; polymers .havinnbetter color,

trifltioroetliyl'ene and vinylidenenfluoridw chlorotrifluoro ethylene and vinyl fluoride chlorotrifluoroethylene and vinyl j chloride, chlbrotrifluoroethylene and viny-lidene chloride, chlorotrifluoroethylene. and.v perfluoropropene, chlorotrifluoroethylene and; trifluoroethylene and per.

fiuorohutadiene;andibutyl acrylate. Incopolymerization. reactions the, secondi'monomebpreferably is also. a fluorinated olefin containing at least two fluorine atoms per. molecule. Whenlessthan 5 weight percentofcomonomer isiempl'oyed, the term copolymerizationis. included withinthe" broad" term. homopol'ymeriza'tion.

The quantity'ofiwater employed as. the aqueous. suspensionmedium may belfiom 1'001tov 800 parts. by weight of water'per I'OUpartsby wei'ghtof total'imonomer; originally present? in the"reaction zone. Preferably, the. quantity. ofwateris from 1100' to300jpa1tsby weight per lOOIparts.

by weight of total monomer. initially present in the reaction zone. p

-Thetemperatures"employedin the polymerization may be-between 0and100 C1 and preferablyarebetween. 5 and' Sl)" O'perationat low temperatures oLpolymerization represents. anothertunique aspect of the present invention, since heretofore when redox catalyst systems were employed; in the'absenceof?azvariableivalence metal salt; it. has; been necessary to operate attemp'eraturesin excess of .50!" G. to .obtainthiglityields.

The: reaction: pressure may be: between 50 and 1200 p. s. i. g., being preferred.

The polymerization time. may be between about 5 hours and 5 days,,,w-ith atime of r 15 to. 25hoursgabeingi range was: to: 2.5;; which-: resulted in rapid' corrosion-- mixture may be between 3' of stainless steel equipment of the polymer product.

The oxidants or promoters which are employed in the process of the present invention are inorganic peroxy compounds, such as sodium carbonate peroxide, sodium pyrophosphate peroxide, sodium persulfate, ammonium persulfate, potassium persulfate, sodium perborate, and the like. These oxidants or promoters may be present in a ratio of 1 to 6 parts by weight per 100 parts of total monomer initially present and are preferably employed in a ratio of 1 to 3 parts by weight per 100 parts by weight of total monomer initially present.

. A buffer or other alkaline material may be employed to adjust the pH of the system to any value within the desired range. Examples of suitable buffers are sodium tetraborate, sodium orthophosphate, sodium acetate, ammonium carbonate, .sodium acetate-acetic acid, and the like.

' The emulsifying agents employed in the present invention are the perfiuorochlorocarboxylic acids and derivatives thereof, having from 6 to 20 carbon atoms. When used as emulsifiers, the'acids are preferably employed in the form of their salts, such as the sodium, potassium, and ammonium salts, but there are additional derivatives of the acids, such as'esters and the like, as hereafter disclosed, which may also be employed.

The perfiuorochlorocarboxylic acids may be employed in a weight ratio of 0.015 to 30 parts per 100 parts of total monomer initially present in the polymerization zone and preferably are employed in a ratio of 1.0 to parts per 100 parts of total monomer initially present.

' The perfluorochlorocarboxylic acids may be produced in a variety of ways. duced by subjecting perhalogenated aliphatic olefins, having at least 7 carbon atoms and being at least half fluorinated, to oxidation conditions in the presence of a vigorous oxygen-containing oxidation reagent, such as free oxygen in the presence of ultra violet light, free oxygen in the presence of ultra violet light and elemental chlorine, free oxygen in the presence of elemental fluorine, and permanganate salts in a liquid medium. Preparation of the acids according to this method is disclosed in copending application Serial No. 452,706, filed August 27, 1954.

' The acids may also be prepared by subjectingv aliphatic perhalogenated high polymers to thermal cracking conditions to produce lower molecular weight materials in the oil and wax range and subjecting the lower molecular weight materials to'oxidation at a temperature not higher than about 10 C. in the presence of a permanganate salt in a liquid medium. Processes of this type are disclosed in copending application Serial No. 452,704 filed August 27, 1954.

Another method for the preparation of perfluorochlorocarboxylic acids useful in the present invention comprises treating fluorine-containing telomers, having the formula M (CF -CX X Br in which M is a perhalomethyl radical having a total atomic weight not higher than 146.5, X and X; are fluorine or chlorine atoms, and n is an integer from 2 to 16, with fuming sulfuric acid at a temperature of at least 125 C. This process produces carboxylic acids having the formula 4 7 Z CF -CF Cl) CF COOH in which Z is a atomic weight not in excess of 146.5 and n is an integer from 2 to 16. The preparation of these acids is dis; closed in copending application Serial No. 452,703, filed August 27, 1954, now Patent No. 2,806,865.

. Acids useful in the process of the invention may also be prepared by hydrolysis of other telomers such as that produced by telomerizing perhaloolefins using-sulfuryl with attendant contamination Serial No. 452,705, filed For example, they may be pro- I acids, it is necessary to reduce the chloride as a telogen, these telomers having the formula Cl(CF CX X,),,Cl in which X; and X; are fluorine or chlorine atoms and n is an integer from 2 to 16. Hydrolysis of these telomers produces moncarboxylic acids having the formula in which X X and n are as given above. The prepara- Serial No. 452,705, filed August 27, 1954, now Patent No. 2,806,866.

The preferred perfluorochlorocarboxylic acids of the invention are those. acids having from 8 to 12 carbon atoms, prepared by the sulfuric acid hydrolysis of the telomeriz'ation product of chlorotrifluoroethylene and mi furyl chloride, as described in copending application August 27, 1954, now Patent No. 2,806,866. These acids have the formula may be employed as emulsifiers in the process of the invention has the formula in which X is fluorine, chlorine, or bromine, n is an in which X; is a perhalomethyl radical having a total atomic weight not in excess of 146.5, and n, m, and R areas given above. The vR above, in addition to a COOH group or a -COOM group, in which M is an alkali metal or ammonium radical, may be a hydrophilic group such as a phosphoric acid group or a sulfuric acid group, --OSO (OM), where M is hydrogen, alkali metal, ammonium, or substituted ammonium; a phosphonic acid group, PO(OM) where M is a as above; or an amine group, e. g., NH or NR where R is alkyl, present as a salt or as a quaternary ammonium compound.

In preparing esters of the above-described carboxylic acid to the alcohol and then react the alcohol with an acid to produce the esters, according to general esterification principles. The perfluorochloroalkyl amines may be prepared by reduction of the corresponding "p'erfiuorochloroalkanoic acid amides, the reducing agent preferably being lithium perhalomethyl radical having a total aluminum hydride used in an anhydrous medium such as absolute ether.

In the preparation of the esters, for example, the reduction, of the acid to'the alcohol results in a CH, group being positioned adjacent to the solubilizing group, as shown in the formulasabove. This CH is present only when the acid is reduced, i. e., when the acid itself is employed or when the acid salts are employed, there is CH, group present.

fAmong the other advantages of the process of the present invention is the fact that high yields at low temperatures of polymerization are realized. Also, stable latices are formed which minimizes polymer buildup on the walls of the reactor and discharge areas, thereby facilitating handling and discharge of the polymer product. I The polymer is also easily wetted with water, thereby facilitatingclea'nup of the polymer product.

An additionaladvantage of using the perfluorochlorocarboxylic acidsof the invention as dispersing or emulsitying agents, results from the fact that the perfluorochlorocarboxylic acid having .8 carbon atoms and prepared by the sulfuric acid hydrolysis of the telomeriza tion product of chlorotrifluoroethylene and sulfuryl. chloride, for example, is soluble in water. This is a useful property, since when polymerization is complete, the latex is coagulated by adding an electrolyte, such as magnesium chloride, magnesium sulfate, aluminum sul fate, concentrated hydrochloric acid, sodium chloride, sodium chloride-sulfuric acid, and the like. Prior to coagulation, the latex is heated to a temperature of 75 to 80 C. and is then coagulated by the addition of magnesium chloride accompanied by vigorous agitation or the latex may be coagulated by freezing. The coagulated polymer is then filtered while hot. The magnesium .salt of Cl (CF -CFCl) CF COOH is soluble in hot water, and thus the coagulated polymer is conveniently and efiiciently freed of the magnesium salt of the acid by washing the polymer with hot water.

Cooling the filtrate precipitates the magnesium salt of C1 (OF -CF01) CF COOH and acidification ofthe magnesium salt regenerates the free acid which can then be recycled to the polymerization zone.

Further, it has been found that the polymers produced by the process of the invention are less susceptible to thermal degradation than those produced in mass polymerization systems, being comparable to pigmented polymers in this regard. v

Finely divided solids may also be dispersed in the liquid phase of the polymerization reaction mixture as a suspension .for the purpose of acting as fillers for the polymer product and for the additional purpose of forming nuclei for the initiation of the polymerization reaction;

The process of the invention also produces polymer products of very high molecular weight, as determined by the no strength temperature (N. S. T.) or 0.75 percent solution viscosity. A no strength temperature (N. S. T.) of between about 210 C. and 350 C. is characteristic ofa normally solid polymer of chlorotrifiuoroethylene having thermoplastic characteristics. The best plastic characteristics of the normally solid polymer are observed at'N. S. T. values between about 240 C. and about 340 C.

The no strength temperature (N. S. T.) is determined in the following manner: A thermoplastic sample of polychlorotrifluoroethylene is hot pressed into a ,6 inch thick sheet and cut into a strip measuring /a inch x hi inch x 1% inches. The strip is notched inch from the top so that the dimension at the notch is 5 inch X A inch. A fine wire and a standard weight are attached to one end of the strip," the weight of the polymer and the wire being 0.5 gram. The strip is then attached vertically in a furnace, and the temperature of the sample is increased at strata of about 1.5 C. per minute as the breaking temperature is approached. The no strength temperature isthe breaking temperature ofthe sample,and difierences of about 5 C. areconsidered significant. r r

Another method for measuring. the molecular weight of polymers is the solution viscosity of a 0.75 percent by weight solution of the tpolymer in 1a 3,5;dichlorobenzotrifluoride solvent. This solution,viscosity is measured in centistokes, and a viscosity oi 0.64 centistokeis equiv ,alent to an N. S. T. of 230. Thus, it will be seen that in the following examples, polymers were produced ac cording to the method of the inventionhaving'very high solution viscosities and, therefore, very high molecular weights. a T

a The invention vwill laeturther illustrated by reference to the following specific examples in. which all parts are by weight:

EXAMPLE 1 This example illustrates the polymerization of chloro trifiuoroethylene using a persulfate- 300.0 CF =CFCl 100.0 Potassium persulfate 1.0-4.0 Cl CFg-CFC1) CF COOH 2.4

A series of runs was carried out in a stainless steel polymerization bomb. In each run the vessel was charged with 300 parts by weight of deionized water, an amount of potassium persulfate as given in Table I below, 2.4 parts of Cl(CF -CFCl) CF COOl-I, enough potassium hydroxide to bring the pH value of the mixture to that given in Table I, and parts by weight of chlorotri fluoroethylene. The bomb was frozen in a solidcar-bon dioxide-acetone bath after the addition of each ingredient and the chlorotrifiuoroethylene was added by flash distilling into the bomb. The closed bomb was tumbled for a period of 20 hours at the temperature indicated in Table I; the bomb was then vented to atmospheric pressure and opened. The polychlorotrifluoroethylene latex Was coagulated by freezing at a temperature between aboutt) and 1 C., the coagulated polymer was filtered, washed thoroughly with hot water and then dried to constant weight at C.

The results are as follows:

Table l 0.75% solution viscosity (cs.)

Kzssos Initial (parts by pH weight) 7 0.

Percent yield Two runs were made using the following persulfatebisulfite Cl(CF V-CFCI) CF COOH acid promoter system.

Parts by weight Water, deionized 300.0 CF =CFCl 100.0 Potassium persulf' ..2.0 Sodium bisulfi 1.1 Cl(CF,-CFCl) CF COOH 2.4

Each run was carried out in a stainless steel polymerization bomb. In each run the vessel was charged with 300 parts by weight of deionized water, 2.0 parts of potassim persulfat'e, 1.1 parts of sodium bisulfite, 2.4l-parts of Cl(CF --CFCl) CF CO0H, enough potassium hydroxide'to blifigfllfi pH of the mixture to that-given in Table 11 below, and 100 parts of chlorotrifluoroethylene, The bomb was frozen in asolid" carbondioxide-acetone bath after the addition of each ingredient and the chlorotrifluoroethylene was added by flash distilling into the bomb. The closed bomb was tumbled for a period of 20 hours ata temperature of. 20 (3.; the bomb was then vented to atmospheric pressure and opened. The latex was-coegulated and dried as described above.

the acid. In the runs in which the buffers, borax and Na HPO were used, each was added in an amount equivalent to 2.4 parts by weight, based on the weight of X monomer. The initial pH values were not measured. 5 Each run was conducted for 20 hours using the same gencvsitywa) eral procedure described in Example 1 above, except that the polymer latex was coagulated using magnesium is a uniform effect of 0th of the acids em pH adjusters employed employ Thus, a

yield by a increase in temperature,

, increases the yield by a ylic acid is acid insofar as yields are n the C ases C acid ing temperatures yield for b perature increasesthe 8 perfluorochlorocarbox the C5 particularly true whe gher concentrations. I perature of the reaction decre and the superiority of the reases with increas while a 10 C.

Percent 0.76

yield Temperature, C.

Table II Initial The results are as follows Run No.

The above data show that there temperature upon the ,-and this is acid is used in the hi Increasing the 'tem the solution viscosity, iz'e 75 over the C5 acid d'ec order to study the etfect of varying the temperature and C,), type of acid (C and C perfiuorochlorol The N.S.T. value as measured for this sample of polyehlorotrifiuoro carboxylic acid having the formula ethylene was Cl(CF CFCl) CF COOH and buifers and pH adjusting materials ployed for all of the butters and "um orthophosphate) on theyield '65 and all of the acid concentratio and solution viscosity ofv the polychlorotrifluoroethylene 1 C. increase in tem e persulfate-perfluorochlorocarboxylic factor of 1.25

. 5 in the-range of 15 to 25 C. All .of the runs were carried out using-300 parts by factor of-9.3. The C parts of CF =CFCL and 2.0 parts more efiicacious than of potassium persulfate. In each run, the potassium salt concerned ylic acid was formed by neupotassium hydroxide. "When po- "pH adjusting. material, it was added; only in an amount suflicient to neutral .3602 633663 743 36168823805 55 43 8531 59 9 34.3 3 1 PW mama awmvdamwua mwwwnmmmwumuwmmnm mwnwmmunamwnmmwnmm HOWOMMTJ LLLLQMLLLZQMLZZKO. LLLLLLLLLLZlLQLLl O.O.LLLL0.L0.0.1.U.O.I.O.O.LL m m. t mm n%%wfififln%%uflwm% nm mmwmwuwwmfimmwm%fl MB7&%WN4MM%M O %MHMM mm QauLaaauaauLLZd uLrlLailtaatatsaz 3d aaaaLlaszLaaals V my l 11 Q1 1 1Q 2 m II" a w w i T m m m PIP" g .u l I HMMHM n E B E E ar r V R R R 80.YB0 W U U U NB KB 0 1M A .9 A A 37273 f T R mmwm R R 0 ua0 u e E. .lwmm E E h P 9 DZ P P t 1 T l M M .m E .u E E e T md T 08080863888888866 T 66 H m CCCCCCCCOOOCCCOCO O0 0 T s n m n a4... m m e o mm u n n n u u U h n u n :u 12 3 45 67 c 12345678911111111 1 L0 0 5 U 5 5 1.0L 1 3 3 4 4 m .0 77 3 m mmawm wm mmmm m m m M24433 emu. .m 1... m m m m sm E m I u m n mmm w I am mumm a m m I mRuI m m a T d SS .1 as i V H S HC W4OY6 he p L T v. H 0 0 .P e gunhlens S e d 3.. NNwm mw mmmwmwmam? m n M T m; m 5.5. H r. n d e ,T m e .16 C H m P a fha Vf B i mm n h A r I m m e e n. d u e eI E T n mm n e m 0 1 m m m m m y t m e w T A n in w u a m a m aa w w m w 5 w ddSnS r. H B h a I n e e .1 H 3 eVJ 'O L U6 d 6 en HS Cb l e .V 6 .1 n .v eno n d .m U S a 3P wd br ad de 8 R 0 rabf at E a U on I RI V E D- 3P .1 E L 3 O ap d o n I A a Pe u rd L mc nr.n.lm .1 E P S LX 77 O CEO P efi fl m roe: P I .m r. P Sd Hr fin C a d e T EN d6 m ifiufimm a; use mmm a ammm gmmmemmm w n Twp. "amnu. mm y e0 aenn a rca se E R n f ehe il E 1 0.] peey a r HT mm. E O em f uu mw dlt R A .1 0 HS .m sa n r r 0m o o A P r u s ws w .mu. w m P am f v n .mmmmmm mm m 8 m w m w w m a m m m m .w u m mm m m .H C e t y g t S m I 1 w a w m m... mm m m m s m P R .s u s 1 n w u B el a m m 0 0 s en wmm m pt m m n m m. m m r t 1 dc n n .n n e blh f hpnv h a I r a O 1 on S t e C pnw m m m w u a a ad a r m m o a v. o. L m mm p m a v m Mmm mdmw mwowmkcmm em. 12345 N M168 W MmW m P C P n n t m fl Q U08 enfi$ weuue P n 1M 0 O f r. H err. U. 0 f. 0 l2 u.mw ohpflomvpanbmmm R N m om u where n is 2 01 3),

(KOH, borax, and so ;.obtained 1 using th .acid system.

weight of water,

'of the perfiuorochlorocarbox .tralizing the acid with ;tasszum hydroxide is listed as the of polymerization. There is no detectable difference between the'buflers employed.

EXAMPLE 4 g This examples illustrates the advantageous use of the bufier sodium monohydrogen orthophosphate in the polymerization of CF =CFCl using a persulfate-perfluorochlorocarboxylic acid promoter system.

A polymerization vessel was charged with 300 parts of deionized water, 2.4 parts of potassium persulfate and 4150 parts of the potassium salt of Cl CF CFCI) CF COOH and 2.4 parts of Na' HPO The intial pH was measured and found to be 8.3. The polymerization reaction was carried out for 20 hours at a temperature of 20 C. following the general procedure of Example 1, above. A 70.0 percent yield of polychlorotrifiuoroethylene, having a 0.75 percent solution viscosity value of 1.152, was obtained. The final pH of the system was 6.8. When the polymerization is conducted in the absence of Na HPO an initial pH value of 7 drops to a final pH value of 3. Thus, in order to keep corrosion problems at a minimum, it is preferable to use sodium orthophosphate (or borax) as a buffer.

EXAMPLE 5 Chlorotrifiuoroethylene was copolymerized 'with vi- .nylidene fluoride using the following recipe:

Parts by weight Water 200.0 CF CFCI 32.6 CF-FCH: 33.8 K 5 M t a I 1.0 Cl(CF CFCl) CF COOH 0.75

The 0.75 part of perfluorochlorocarboxylic acid was dissolved in 100' parts of deionized water by neutralizing the acid with a 2.5 percent potassium hydroxide solution to pH 7. This solution was diluted to 150 parts and frozen in a stainless steel bomb after which 1'00 parts of water, containing 1 part of potassium .persulfate, were added to the bomb, the contents of whichwere refrozen, and 32.6 parts of chlorotrifluoroethylene and 33.8 parts of vinylidene fluoride, representing a total monomer charge containing 35 mole percent of chlorotrifiuoroethylene and 65 mole percent of vinylidene fluoride, were also charged to the bomb. The bomb was closed, warmed to a temperature of +5 C. and tumbled for 24 hours. The residual monomers were vented from the bomb and the polymeric latex was discharged, coagulated with sodium chloride-acid solution, filtered, washed with cold water and then hot, and dried in vacuo at a temperature of 35 C. A 41 percent yield of a chlorotrifluoroethylene-vinylidene fluoride copolymer was obtained having a 0.75 percent solution viscosity value, as determined in a 3,5-dichlorobenzotrifluoride solvent, of 1.164 centistokes.

EXAMPLE 6 A series of runs was made to determine the effect of the surface tension of the aqueous polymerization system upon the yield of polymer produced.

The following recipe was used to conduct the polymerizations:

Parts by weight Temperature, 25 C. Time, 20 hours.

g The results are as follows:

Table VI Gl(CFa- 0.75% CF01) Surface Percent solution Run No. CFgCOOH tension, yield viscosity (parts by dynes/om. (05.)

we t

None 60. 2 0 30 46. 3 6. 36 1. 193 0. 75 37. 5 12. 84 1. 161 2. 25 29. 2 36. 7 11260 4. 50 28. 3 70. 0 1. 315 7. 50 27. 6 81. 8 1. 398

1 Surface tension measured on recipe before polymerization, without l 1 1%ion viscosity measured in 3,5-diclilorobenzotrlfluorlde solvent.

The above data show that as the surface tension of the aqueous polymerization system is decreased, the yield of polymer product is correspondingly increased. The halogenated acid decreases the surface tension resulting in increased contact between the monomer and the aqueous phase, thereby augmenting the yield of polymer product.

A sample of polychlorotrifiuoroethylene prepared in an acid-free persulfate system failed the embrittlement test after heat aging at a temperature of C. for a period of three days, while the sample of. polychlorotrifluoroethylene prepared using a C telomer acid persulfate system passed the same embrittlement test after heat aging at a temperature of 190 C. for a periodof .28 days. The molecular weight of this sample, as determined by osmotic pressure measurement, was 175,000.

It will be obvious'to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit there of, and the invention includes all such modifications.

We claim:

1. A process which comprises polymerizing at least one but not more than two halogenated polymerizable ethylenically unsaturated monomers in the presence of a system containing substantially no added redu'ctant being maintained at a temperature between about 5 and about 30'? C. and having an initial pH between about 6 and 10 and consisting essentially of water, an inorganic peroxy compound, and a compound having the formula in which X is selected from the group consisting of fluorine, chlorine, bromine and a perhalomethyl radical having a total atomic weight not in excess of 146.5, n is an integer from 2 to 9, R is a solubilizing group, and m is selected from the group consisting of 0 and 1 and is 0 only when R contains a 2. A process which comprises polymerizing at least one but not more than two halogenated polymerizable ethylenically unsaturated monomers in the presence of a system containing substantially no added reductant, being maintained at a temperature between about 5 and about 30 C. and having an initial pH between about 6 and 10 and consisting essentially of water, an inorganic peroxide, and a compound having the formula in which X is selected from the group consisting of fluorine, chlorine, and bromine, n is an integer from 2 to 9, R is a solubilizing group, and m is selected from the group consisting of 0 and l and is 0 only when R contains a p group.

in which n is an integer from 2 to 9 and R is a solubilizing group.

4. A process which comprises polymerizing at least one but not more than two halogenated polymerizable ethylenically unsaturated monomers in the presence of a system containing substantially no added reductant, being maintained at a temperature between about 5 and about 30 C. and having an initial pH between about 6 and and consisting essentially of water, an inorganic peroxide, and I I a compound having the formula Cl(CF CFCl) CF -COOM in which n is an integer from 2 to 9 and M is selected from the group consisting of metal cations and ammonium groups.

5. A process which comprises polymerizing at least one but not more than two halogenated polymerizable ethylenically unsaturated monomers in the presence of a system containing substantially no added reductant and maintained at a temperature between about 5 and about C. and at an alkaline pH and consisting essentially of water, an inorganic peroxide, and between about 1 and about 10 parts per 100 parts of monomer, a compound having the formula a in which M is a metal cation.

6. A process which comprises polymerizing at least one but not more than two halogenated polymerizable ethylenically unsaturated monomers in the presence of a system containing substantially no added reductant, being maintained at a temperature between about 5 and about C. and having an initial pH between about 6 and 10 and con- .sisting essentially of water, an inorganic peroxide, and a compound having the formula in which X is a perhalomethyl radical having a atomic weight not in excess of 146.5, n is an integer from 2 to 9. R is a solubilizing group, and m is selected from the group consisting of 0 and 1 and is 0 only when R contains a v 7. A process which comprises polymerizing at least one but not more than two halogenated polymerizable ethyleni-cally unsaturated monomers in the presence of a system containing substantially no added reductant, being maintained at a temperature between about 5 and about 30 C. and having an initial pH between about 6 and 10 and consisting essentially of water, an inorganic peroxide, and a compound having the formula in which n is an integer from 2 to 9 and R is a solubilizing group.

8. A process which comprises polymerizing at least one but not more than two halogenated polymerizable ethylenically unsaturated monomers in the presence of a system containing substantially no added reductant, being maintained at a temperature between about 5 and about 30 C. and having an initial pH between about 6 and 10 and consisting essentially of water, an inorganic peroxide, and a compound having the formula groups.

References Cited in the file of this patent UNITED STATES PATENTS 2,559,752 Berry July 10, 1951 2,612,484 Bankoff Sept. 30, 1952 2,613,202 Roedel Oct. 7, 1952 2,689,241 Dittman Sept. 14, 1954 2,766,215 Stoops et a1 Oct. 9, 1956 

1. A PROCESS WHICH COMPRISES POLYMERIZING AT LEAST ONE BUT NOT MORE THAN TWO HALOGENATED POLYMERIZABLE ETHYLENICALLY UNSATURATED MONOMERS IN THE PRESENCE OF A SYSTEM CONTAINING SUBSTANTIALLY NO ADDED REDUCTANT BEING MAINTAINED AT A TEMPERATURE BETWEEN ABOUT 5 AND ABOUT 30*C. AND HAVING AN INITIAL PH BETWEEN ABOUT 6 AND 10 AND CONSISTING ESSENTIALLY OF WATERS, AN INORGANIC PEROXY COMPOUND, AND A COMPOUND HAVING THE FORMULA 